The present invention relates to the positioning and adjusting of rolles within an oblique roll rolling mill, particularly of the type using three rolls with generally conical rolling surfaces having axes which are oriented relative to the axes of the rolled stock at a rather large angle and appearing as a spreading angle or angle of spread which opens in the direction of rolling.
The so called high reduction oblique roll rolling mills are known also in a variety called planetary type oblique rolling mills with a rotating rolling frame and a non-rotating tube. Alternatively oblique constructed as a three roll rolling mill with conical rolling surfaces and inclined axes, for a high degree of reduction of tubes and having a stationary rolling stand and rotating tubular hollow. In all cases one has to consider the smooth bore requirement for the hollow to be made. This follows from the fact, that any of these high reduction rolling mills, for purposes of manufacturing particular wall thickness tolerances constitute already a final stage, i.e. no further deforming with an interior tool or the like is necessary (or should be). Therefore any surface undulation or waviness which is typical for oblique rolling processes generally and is manifested as local wall thickness variation of helical configuration cannot be tolerated, particularly if the wall thickness is rather thin to begin with.
The same requirement for obtaining a smooth bore is also posed in the so called Assel rolling mills, but with the difference that stretching and feed advance are very small, so that the spacial orientation of the rolling axes exhibits only a very small angle relative to the axes of the rolles stock. This means that the smooth bore effect in the case of a dimension depending roll adjustment is controllable only to a very minimal extent.
The situation is quite different for socalled high reduction oblique rolling mills, wherein a hollow billit is stretched through utilization of a cylindrical mandrel rod for purposes of obtaining a hollow tube. Very large stretch values are feasible resulting for these kinds of rolling mills from the rather favorable operational conditions referring to the speed, which in turn are the consequence of the particular spacial disposition of the rolls. It is thus of no consequence that in the case of a planetary, oblique axes rolling mills, the rolls in fact revolve about the tube in a planetary type movement, while in the case of a three roll mill with conical rolls the tube rotates.
Therefore in the following only the rotating stock will be described, and only one of the three rolls are considered; any extension of the concept particularly with regard to the relative aspects of rotation follow logically from these considerations.